• About This Guide
  
• How This Guide is Being Developed
  
• Philosophy of this guide
  
• Using this Guide
  
• Thinking Scientifically
  
• About the Author
  
• Documented Genes
  
• What is a documented gene?
  
• Black/Red (MC1R)
  
• Bay (ASIP)
  
• Cream/Pearl (SLC45A2)
  
• Dun (TBX3)
  
• Gray (STX17)
  
• Silver (PMEL17)
  
• Champagne (SLC36A1)
  
• Roan/Tobiano/Sabino/White Spotting (KIT)
  
• Splash White (MITF/PAX3)
  
• Leopard Complex (TRPM1/ECA3P)
  
• Frame (EDNRB)
  
• Tiger Eye (SLC24A5)
  
• Height Regulation (HMGA2/LCORL)
  
• Mushroom (MFSD12)
  
• Hypothetical Genes
  
• What is a hypothetical gene?
  
• Borrowed Genes
  
• Glossaries
  
• Glossary of Colors
  
• Glossary of Terms
  

Mushroom (MFSD12)

• Last updated: 2026-01-19

  Common Names: Mushroom

  Scientific Name: major facilitator superfamily domain containing 12 (MFSD12 )

  Equine Chromosome: 7

  General Overview:

  Mushroom is a dilution gene that impacts red pigment only and is found in Shetland Ponies. It is recessive and requires two copies to show. Mushroom horses have a sepia tone similar to a crimini mushroom with e/e individuals often having flaxen manes and tails. Bay horses can show a mild dilution in the brown areas of their coat. It has no known impact on black horses. [1]

• Citations:

  1. Tanaka J, Leeb T, Rushton J, Famula TR, Mack M, Jagannathan V, Flury C, Bachmann I, Eberth J, McDonnell SM, Penedo MCT, Bellone RR. Frameshift Variant in MFSD12 Explains the Mushroom Coat Color Dilution in Shetland Ponies. Genes (Basel). 2019 Oct 19;10(10):826. doi: 10.3390/genes10100826. PMID: 31635058; PMCID: PMC6827053.
     https://pubmed.ncbi.nlm.nih.gov/31635058/

• Examples:

  Chestnut e/e Mu/?, Chestnut Mushroom e/e mu/mu

  

  
  

  Bay e/e Mu/?, Bay Mushroom e/e mu/mu